参数类型“Map<String, Object>”不能分配给参数类型“String”答案

【问题标题】：The argument type 'Map<String, Object>' can't be assigned to the parameter type 'String'参数类型“Map<String, Object>”不能分配给参数类型“String”
【发布时间】：2021-08-20 15:19:03
【问题描述】：

import 'package:learnflutter/questionMain.dart';
import 'questionButton.dart';

class mainQuestions extends StatelessWidget {
  List aQuestions;
  int questionIndex;
  Function answerQuestion;

  mainQuestions(
      {required this.aQuestions,
      required this.answerQuestion,
      required this.questionIndex});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          aQuestions[questionIndex]['aQuestion'],
        ),
        ...(aQuestions[questionIndex]['answers'] as List<Map<dynamic, dynamic>>)
            .map((answer) {
          return Answer(answerQuestion, answer);
        })
      ],
    );
  }
}

我的问题是它一直在说：参数类型“Map”不能分配给参数类型“String” 我是新来的颤振有人能帮助我吗？谢谢！（不是说要使用 HTML 只是不知道如何添加代码）

...(aQuestions[questionIndex]['answers'] as List<Map<dynamic, dynamic>>)
            .map((answer) {
          return Answer(answerQuestion, answer);

【问题讨论】：

标签： arrays list flutter dart

【解决方案1】：

我认为将解决的问题是将答案提取到一个单独的变量中，并在最后调用toList。这并没有对我产生任何编译错误：

List<Widget> _answers() {
  List<Map<dynamic, dynamic>> answers = aQuestions[questionIndex]['answers'] as List<Map<dynamic, dynamic>>;
  return answers.map(answer => Answer(answerQuestion, answer)).toList();
}

return Column(
  children: [
    Question(aQuestions[questionIndex]['aQuestion']),
    ..._answers(),
  ]

【讨论】：

【解决方案2】：

map 函数返回一个可迭代的，而不是一个列表。这就是为什么在映射之后，您必须通过调用其 toList() 函数将其转换为列表。方法如下：

import 'package:learnflutter/questionMain.dart';
import 'questionButton.dart';

class mainQuestions extends StatelessWidget {
  List aQuestions;
  int questionIndex;
  Function answerQuestion;

  mainQuestions(
      {required this.aQuestions,
      required this.answerQuestion,
      required this.questionIndex});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          aQuestions[questionIndex]['aQuestion'],
        ),
        ...(aQuestions[questionIndex]['answers'] as List<Map<dynamic, dynamic>>)
            .map((answer) {
          return Answer(answerQuestion, answer);
        }).toList()
      ],
    );
  }
}

【讨论】：